The present invention relates generally to storage systems and, more particularly, to hierarchy memory management between server and storage system using RDMA (Remote Direct Memory Access) technology.
Remote memory access and allocation technology such as RDMA (Remote Direct Memory Access) is available. One approach involves dynamic memory management in an RDMA context (see, e.g., U.S. Pat. No. 7,849,272). Another approach involves distributed shared memory on a plurality of computers (see, e.g., US2009/0144388). Server attached PCI-Express™ flash is cheaper bit cost than large capacity RDIMM (Registered Dual Inline Memory Module) module.
A server has limited physical memory capacity which depends on the CPU architecture. To expand the capacity of Server DRAM (Direct Random Access Memory), RDIMM (Registered Dual Inline Memory Module) is required. Large capacity RDIMM is highest cost of any other DIMM type. Server DIMM socket is not hot swappable. To expand the memory capacity of the server, the server administrator stops the OS (Operation System) and stops power to the server, and then the server administrator installs DIMM to DIMM slot of the motherboard.
Local server memory provides higher performance than remote memory access by RDMA (Remote Direct Memory Access), since DDR SDRAM (Double-Data-Rate Synchronous Dynamic Random Access Memory) interface has higher access latency and capacity of network throughput than RDMA network. DRAM has lower access latency than flash memory. Conventional technology does not disclose (1) which type of local memory or remote memory is better hierarchy for performance and (2) which type of DRAM, flash memory, or other new memory device has the best hierarchy of DRAM memory tier. Also, current memory allocation of RDMA protocol does not provide memory type information.
Cache memory of storage system constitutes DRAM and/or flash memory. Current storage system does not share memory of storage system as both of storage cache and server memory expansion.